ABSTRACT In response to the emerging COVID-19 (SARS-CoV-2) pandemic, this supplement proposal to R44 AI138733- 01 will leverage our cutting-edge nucleic acid vaccine strategies, some of which that were developed under this parent grant. Here, we request supplement funding to develop candidate COVID-19 DNA and RNA vaccines expressing optimally designed immunogens for the SARS-CoV-2 spike protein. Nucleic acid (DNA and RNA) vaccines offer significant promise for providing a rapid response solution to emerging infectious diseases because only a partial genetic sequence of the pathogen is needed to generate a new vaccine. Following in vivo delivery, DNA and RNA vaccines lead to in situ production of antigens, negating the need for a complex manufacturing and process development required for purified recombinant protein, inactivated or live attenuated vaccines. Nucleic acids can also be manufactured at low cost and are very stable at room temperature eliminating the need for a cold chain. This provides a significant savings in the time needed to advance a new vaccine from identification of genetic sequence to clinical testing and distribute it to the population. In addition, possibly due to the ability of nucleic acid vaccines to present antigens in their natural conformation in vivo, antibody responses are generally of higher avidity and broader specificity when compared to antibody induced by subunit protein vaccines. Further, the intracellular expression of antigens also induces robust T cell responses including potent CD8+ T cell responses that can more broadly recognize different viral strains and mediate protection via enhanced clearance of the infection. Our approach will compare our optimized DNA and RNA vaccine platform technologies alone and in combinations to identify a lead approach that induces the highest and most rapid development of protective levels of neutralizing antibody after a single administration. In addition, since nucleic acid vaccines tested in our lab have been shown to induce antibody and/or T cell responses that induce cross-protective immunity in our universal influenza vaccine studies under our parent grant, we will determine if the candidate vaccines exhibit cross reactivity against other coronavirus strains for broader protection against future coronavirus strains with epidemic or pandemic potential. Our Aims include: Aim 1- Design and compare immunogenicity of candidate SARS-CoV-2 DNA and RNA vaccines. Aim 2 - Maximize immunogenicity of nucleic acid vaccines and rapid manufacture by combining DNA and replicon mRNA vaccines together or with recombinant protein and optimizing DNA and mRNA formulations. Aim 3 - Safety and immunogenicity of the lead COVID-19 nucleic acid protein vaccine in the preclinical nonhuman primate model. If successful, should identify a lead candidate COVID-19 nucleic acid vaccine for phase I human clinical trials.